diff --git a/lib/Parser/JSParserImpl-flow.cpp b/lib/Parser/JSParserImpl-flow.cpp
index bf9d2896736..f60f2df0b88 100644
--- a/lib/Parser/JSParserImpl-flow.cpp
+++ b/lib/Parser/JSParserImpl-flow.cpp
@@ -2345,7 +2345,7 @@ Optional<ESTree::Node *> JSParserImpl::parseReturnTypeAnnotationFlow(
     if (!optType)
       return None;
 
-    if (check(TokenKind::identifier)) {
+    if (check(TokenKind::identifier, TokenKind::rw_this)) {
       // Validate the "implies" token was an identifier not a more complex type.
       if (auto *generic = dyn_cast<ESTree::GenericTypeAnnotationNode>(*optType);
           !(generic && !generic->_typeParameters)) {
@@ -2360,8 +2360,8 @@ Optional<ESTree::Node *> JSParserImpl::parseReturnTypeAnnotationFlow(
       ESTree::Node *id = setLocation(
           tok_,
           tok_,
-          new (context_)
-              ESTree::IdentifierNode(tok_->getIdentifier(), nullptr, false));
+          new (context_) ESTree::IdentifierNode(
+              tok_->getResWordOrIdentifier(), nullptr, false));
       advance(JSLexer::GrammarContext::Type);
 
       //   implies IdentifierName is TypeAnnotation
diff --git a/test/Parser/flow/predicate-implies.js b/test/Parser/flow/predicate-implies.js
index 1bd26b0d596..ae172a980a9 100644
--- a/test/Parser/flow/predicate-implies.js
+++ b/test/Parser/flow/predicate-implies.js
@@ -540,7 +540,35 @@ type T = (empty: mixed) => implies empty is number;
 // CHECK-NEXT:         "rest": null,
 // CHECK-NEXT:         "typeParameters": null
 // CHECK-NEXT:       }
-// CHECK-NEXT:     }
+// CHECK-NEXT:     },
+
+type T = () => implies this is number;
+// CHECK-NEXT: {
+// CHECK-NEXT:   "type": "TypeAlias",
+// CHECK-NEXT:   "id": {
+// CHECK-NEXT:     "type": "Identifier",
+// CHECK-NEXT:     "name": "T"
+// CHECK-NEXT:   },
+// CHECK-NEXT:   "typeParameters": null,
+// CHECK-NEXT:   "right": {
+// CHECK-NEXT:     "type": "FunctionTypeAnnotation",
+// CHECK-NEXT:     "params": [],
+// CHECK-NEXT:     "this": null,
+// CHECK-NEXT:     "returnType": {
+// CHECK-NEXT:       "type": "TypePredicate",
+// CHECK-NEXT:       "parameterName": {
+// CHECK-NEXT:         "type": "Identifier",
+// CHECK-NEXT:         "name": "this"
+// CHECK-NEXT:       },
+// CHECK-NEXT:       "typeAnnotation": {
+// CHECK-NEXT:         "type": "NumberTypeAnnotation"
+// CHECK-NEXT:       },
+// CHECK-NEXT:       "kind": "implies"
+// CHECK-NEXT:     },
+// CHECK-NEXT:     "rest": null,
+// CHECK-NEXT:     "typeParameters": null
+// CHECK-NEXT:   }
+// CHECK-NEXT: }
 
 // CHECK-NEXT:   ]
 // CHECK-NEXT: }
diff --git a/test/Parser/flow/predicate-method-return.js b/test/Parser/flow/predicate-method-return.js
index 48816031b68..3ca9fdd4012 100644
--- a/test/Parser/flow/predicate-method-return.js
+++ b/test/Parser/flow/predicate-method-return.js
@@ -326,6 +326,116 @@ class C { m(): this is T {} }
 // CHECK-NEXT:       }
 // CHECK-NEXT:     ]
 // CHECK-NEXT:   }
+// CHECK-NEXT: },
+
+class C { m(): implies x is T {} }
+// CHECK-NEXT: {
+// CHECK-NEXT:   "type": "ClassDeclaration",
+// CHECK-NEXT:   "id": {
+// CHECK-NEXT:     "type": "Identifier",
+// CHECK-NEXT:     "name": "C"
+// CHECK-NEXT:   },
+// CHECK-NEXT:   "superClass": null,
+// CHECK-NEXT:   "body": {
+// CHECK-NEXT:     "type": "ClassBody",
+// CHECK-NEXT:     "body": [
+// CHECK-NEXT:       {
+// CHECK-NEXT:         "type": "MethodDefinition",
+// CHECK-NEXT:         "key": {
+// CHECK-NEXT:           "type": "Identifier",
+// CHECK-NEXT:           "name": "m"
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "value": {
+// CHECK-NEXT:           "type": "FunctionExpression",
+// CHECK-NEXT:           "id": null,
+// CHECK-NEXT:           "params": [],
+// CHECK-NEXT:           "body": {
+// CHECK-NEXT:             "type": "BlockStatement",
+// CHECK-NEXT:             "body": []
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "returnType": {
+// CHECK-NEXT:             "type": "TypeAnnotation",
+// CHECK-NEXT:             "typeAnnotation": {
+// CHECK-NEXT:               "type": "TypePredicate",
+// CHECK-NEXT:               "parameterName": {
+// CHECK-NEXT:                 "type": "Identifier",
+// CHECK-NEXT:                 "name": "x"
+// CHECK-NEXT:               },
+// CHECK-NEXT:               "typeAnnotation": {
+// CHECK-NEXT:                 "type": "GenericTypeAnnotation",
+// CHECK-NEXT:                 "id": {
+// CHECK-NEXT:                   "type": "Identifier",
+// CHECK-NEXT:                   "name": "T"
+// CHECK-NEXT:                 },
+// CHECK-NEXT:                 "typeParameters": null
+// CHECK-NEXT:               },
+// CHECK-NEXT:               "kind": "implies"
+// CHECK-NEXT:             }
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "generator": false,
+// CHECK-NEXT:           "async": false
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "kind": "method",
+// CHECK-NEXT:         "computed": false,
+// CHECK-NEXT:         "static": false
+// CHECK-NEXT:       }
+// CHECK-NEXT:     ]
+// CHECK-NEXT:   }
+// CHECK-NEXT: },
+
+class C { m(): implies this is T {} }
+// CHECK-NEXT: {
+// CHECK-NEXT:   "type": "ClassDeclaration",
+// CHECK-NEXT:   "id": {
+// CHECK-NEXT:     "type": "Identifier",
+// CHECK-NEXT:     "name": "C"
+// CHECK-NEXT:   },
+// CHECK-NEXT:   "superClass": null,
+// CHECK-NEXT:   "body": {
+// CHECK-NEXT:     "type": "ClassBody",
+// CHECK-NEXT:     "body": [
+// CHECK-NEXT:       {
+// CHECK-NEXT:         "type": "MethodDefinition",
+// CHECK-NEXT:         "key": {
+// CHECK-NEXT:           "type": "Identifier",
+// CHECK-NEXT:           "name": "m"
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "value": {
+// CHECK-NEXT:           "type": "FunctionExpression",
+// CHECK-NEXT:           "id": null,
+// CHECK-NEXT:           "params": [],
+// CHECK-NEXT:           "body": {
+// CHECK-NEXT:             "type": "BlockStatement",
+// CHECK-NEXT:             "body": []
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "returnType": {
+// CHECK-NEXT:             "type": "TypeAnnotation",
+// CHECK-NEXT:             "typeAnnotation": {
+// CHECK-NEXT:               "type": "TypePredicate",
+// CHECK-NEXT:               "parameterName": {
+// CHECK-NEXT:                 "type": "Identifier",
+// CHECK-NEXT:                 "name": "this"
+// CHECK-NEXT:               },
+// CHECK-NEXT:               "typeAnnotation": {
+// CHECK-NEXT:                 "type": "GenericTypeAnnotation",
+// CHECK-NEXT:                 "id": {
+// CHECK-NEXT:                   "type": "Identifier",
+// CHECK-NEXT:                   "name": "T"
+// CHECK-NEXT:                 },
+// CHECK-NEXT:                 "typeParameters": null
+// CHECK-NEXT:               },
+// CHECK-NEXT:               "kind": "implies"
+// CHECK-NEXT:             }
+// CHECK-NEXT:           },
+// CHECK-NEXT:           "generator": false,
+// CHECK-NEXT:           "async": false
+// CHECK-NEXT:         },
+// CHECK-NEXT:         "kind": "method",
+// CHECK-NEXT:         "computed": false,
+// CHECK-NEXT:         "static": false
+// CHECK-NEXT:       }
+// CHECK-NEXT:     ]
+// CHECK-NEXT:   }
 // CHECK-NEXT: }
 
 // CHECK-NEXT:   ]